Safety system for electric plants



March 3, 1931-- o. Hl-:lNlscH ET AL 1,794,586

SAFETY SYSTEM FOR ELECTRIC PLANTS Filed NOV. 20, 1928 im 4mm@ Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE OTTO HEINISCH, OF OBRIGHOVEN, NEAR WESEL, AND ANTON RIEDL, OF FLUREN, NEAR WESEL, GERMANY SAFETY SYSTEM FOR ELECTRIC PLANTS Application led November 20, 1928, Serial No. 320,584, and in Germany October 7, 1927.

invention relates to improvements in safety systems for electric plants, and 'the object of the improvements is to provide a system for immediately disconnecting the 5 conductors normally connected with the supply of electric energy from the said supply whenever contact is made with one of the conductors. Vsith this obj ect in view our invention consists in connecting two conductors of the system, tor example two outer conductors or phase conductors, or an outer conductor and the neutral conductor with the ground by means of leads each including a coil or" l yitch adapted to disconnect the system from tl'ie current supply. In carrying out the invention either 1ooth coils included in the said are combined in a single switch or each coil is provided in a switch of its own, one oi the switches being for example a hightension switch and the other one a lo v-ten sion switch. Thus the resistance of the said leads connecting the conductors with the ground is such that a current successively flowing through both leads from one phase conductor to the other one or from the phase conductor to the neutral conductor is not able to operate the switch, while the current flowing through one of the said coils is adapted to operate the switch. Instead of providing 33 two separate leads for connecting the conductors with the ground a single earth connection may be provided which is connected between the said coils of the switch or switches to the lead connecting the outer wires or an outer wire and the neutral wire.

For the purpose of explaining the invenvention an example embodying the same has been shown in the accompanying drawing in which the same reference characters have been used in all the views to indicate corrcspending parts. ln said drawing,

`Fig. l, is a diagram showingr a net provided with our improved safety system, and Fig. 2, is a diagram showing the position of t ie asymmetric units in the netA -In the example shown in l the net comprises three phase conductors T, S, T and a neutral conductor O, the said conductors including a transformer e and two switches h and c, the switch being located yand a testine' switch 7i.

in the hi g; i-tension conductors and the switch c in the lowtension conductors of the transformer. The phase conductor T is connected by a lead la including switch coils l and e and resistances f and g with the neutral conductor. To a point intermediate the coils d and c a grounded lead z' is connected. Further7 the phase conductor S is grounded through lead m including a resistance n Similar subsidiary switches may be provided at any part of the plant as emergency switches.

The lead is continuously energized by a certain current, which however is small by reason of the resistanc'es included in the lead, and which therefore is not sufficient to opcrate the switches 7) and c. If however one of the conductors O or T is connected to the ground for example by a person making Contact therewith the resistance g and coil e or resistance f and coil d are short-circuited, and the current flowing through the coil which has not been short-circuited is sufficient to operate the switch and to disconnect the net from the current supply. Vhen making a ground contact with the conductor R or'S the current flowing through both switch coils is increased. The neutral conductor is insulated from the ground, because the safety system is operated also when the neutral wire is grounded, by reason of the earth connection of the outer wire.

Tf in alternating current distribution plants the continuous energizing of the coils CZ and e is not desired asymmetric units a: and g/ may be included in the branches of the lead 7c which permit the flow of the current in one direction only and which are included in the said branches so as to be directed in opposition to each other. Thus no current can iow from phase conductor to phase conductor or from phase conductor to neutral conductor, but there is only a flow of current from the ground if the phase conductor or the neutral conductor is grounded.

The conductors are disconnected from the current supply whenever one of the wires is grounded, for example when a person makes contact with one of the phase conductors, in which case the current flowing through one of the coils CZ or e or the current flowing through both coils CZ, e is increased. The constructioncan be made so Vthat the net is disconnected within less than l of a second, which time is so short that any injury by the grounding of the conductor is avoided, Since the system is switched out also by an earth or body contact, special satety means for metallic parts which normally are not energized are not necessary'.

The operation of the system can be tested at any time by means of the testing switches h or u adapted to ground one of the conductors and to throw one or both s 7itches into operation.

We claim:

l. ln an electrical distribution system, einbodying two conductors and source of curl rent supply therefor, leads connecting said conductors with the ground, and switches each one of which is controlled by the current' througheach or said'leads for disconnecting said conductors from the current sup- Plif- Y p f 2. In an electrical distribution system, enibcdying a plurality of main conductors, source or current supply for the conductors, leads connecting at least two of said conductors with the ground, and switches each one of which iscontrolled by the current from each of said leads Vfor disconnecting said conductors from the current supply.

3. In anelectrical distribution system, einbodying a plurality of main conductors and neutral conductor, a source of current supply, leads connecting one of saidV inainvconductors and said neutral conductor with the ground, and switches associated with said leads, each switch being connected to be controlled bythe current from each civ said leads for disconnecting said main conductors and neutral conductor from the source of supply. Y il. ln an electrical distribution system, einbodying two conductors and a source of current supply therefor, leads connecting said conductors Vwith the ground, resistances included in said leads, switches with coils included in the leads atvpoints on the ground side of the'resistances, each (switch, by the energization` of its coil by current from each of said leads, being controlled to disconnect said conductors from the current supply.

5. In an electrical distribution system, ein-V bodying two'conductorsand a source 'of current supplytherefor, a grounded lead, branch leads connecting saidv grounded lead with said conductors, and a switchin each branch lead controlled by current from each of said branch leads Vfor disconnecting said con ductors from the current supply.v

' 6. In an-electrical distribution system, enibodying two conductors vand a source of current supply therefor, leads connecting said conductors with the ground, a switch under the control of the current through said leads Y our signatures.

OTT() HENISCH. NTN REDL. 

